Method of duplex puddling



April 10, 1934. c. HART METHOD OF DUPLEX PUDDLING 2 Sheets-Sheet 1 Filed March 10. 1930 April 10, 1934. c. HART METHOD OF DUPLEX PUDDLING Filed March 10. 1930 2 Sheets-Sheet 2 Patented Apr. 10, 1934 UNITED STATES METHOD OF DUPLEX PUDDLING Charles Hart, Media, Pa., assignor, by mesne assignments, of one-half to William Steell Jackson, Philadelphia, Pa.

Application March 10,

14 Claims.

My invention relates to methods and apparatus for making wrought iron.

The main purpose of my invention is to separate the operation of making wrought iron into two steps, in the first of which substantially all the manganese and silicon removal may take place without seriously affecting the carbon and preferably without seriously decreasing the phosphorus content, so that the phosphorus may protect the carbon; and in the second of which the phosphorus intended to be removed may be taken out, and a carbon content in excess of 1% may be used to secure a vigorous boil.

A further purpose is, in the making of wrought iron, to remove the manganese and silicon as a preliminary operation in a furnace under acid conditions, so that their removal may not unduly affect the content of phosphorus and carbon.

A further purpose is to utilize a shallow hearth acid reverberatory furnace for preliminary clearing of cast iron from silicon and manganese under quiescent conditions before puddling.

A further purpose in the duplex manufacture of wrought iron is to clear of manganese and silicon in an acid lined furnace subjected to surface fuel heating, as distinguished from a converter.

In duplexing wrought iron 2. further purpose is to remove the manganese and silicon in a first step along with the slag resulting from this operation, in order that the slag within the furnace in which the second step is performed may be more perfectly controlled, and the character as well as the quantity of slag in the resultant wrought iron may be closely predetermined and regulated.

A further purpose is to vigorously boil and work thoroughly a furnace charge initially nearly free from manganese and silicon to be oxidized or already oxidized from the metal and in which the carbon content preferably closely approximates that of the original uncleared iron and in any case exceeds 1%.

A further purpose is to operate upon an iron content substantially free from manganese and silicon which are not to go into the finished muck bar, initially draining 01f slag which has come over from the process of clearing of these elements, utilizing a new basic oxidizing slag to decrease the content of or eliminate the phosphorus, and boiling the slag containing the phosphorus, but nearly free from manganese and silicon to be oxidized or already oxidized from the metal, in with the iron.

A further purpose is to maintain an iron bath 1930, Serial No. 434,697

substantially quiescent at moderate temperature in a basic lined mechanical puddling furnace to remove phosphorus from the iron before boiling, preferably using a slag high in iron cinder and low in roll scale.

A further purpose is to mechanically puddle a charge in which the manganese and silicon to be removed have been taken out in a previous process, and, preliminary to mechanical puddling, to separate the slag from the iron after this manganeseand silicon-clearing process so as to secure a more ductile slag fiber than is practicable in hand-puddling.

A further purpose is to utilize a puddling furnace slag primarily designed with a View tothe physical properties of the solidified slag when incorporated into the muck bar, rather than with reference to its eifectiveness in clearing the iron of impurities.

A further purpose is to control the percentage of phosphorus in the slag and in the iron by controlling the slagging additions to the charge, and by controlling the operating temperature and selective action of oxygen.

In mechanical puddling a further purpose is to Work the iron until it begins to come to nature and, before balling and while working, to drain 01f the remaining localized slag by decantation from the iron.

A further purpose is to boil an iron substantially free from manganese and silicon and high manganese slag, while pouring the iron about the lining of a mechanical mixer to turbulently mix it.

Definitions As there is some looseness of language or lack of clear definition as to what is meant by some of the terms in the ferrous metallurgical art, I have aimed in the present specification to clear from this by the following nomenclature:

The raw iron upon which I intend to operate is called by me uncleared iron, whether it be taken direct in molten condition from a blast furnace or from a cupola or storage bath, or whether it be solid pig iron remelted in my own first furnace or in another furnace. Uncleared iron will contain when molten at least 1% of carbon and ordinarily more than 3% of carbon, along with other impurities. Scrap could be used to a certain extent, and to that extent I intend it to be included in my definition as uncleared iron. Uncleared iron inmolten condition, whether it is charged molten or charged cold and melted in the furnace, is called by me molten uncleared iron.

. iron.

The first steps in my operation are the partial clearing of this iron to remove manganese and silicon wholly or in part according to the composition desired, or which can be secured for the ultimate iron. This partially cleared product, whether the manganese and silicon be initially low enough or has been reduced by my first steps, or in any other way, I call manganeseand silicon-cleared iron. It will be understood, of course, that some manganese and silicon will ordinarily still remain in this material, as it is desired in the finished product according to many specifications.

The iron thus normally resulting from the operation within my first furnace, which is the raw product for my second furnace, is considered as manganeseand silicon-cleared iron up to the point in the second furnace where phosphorus is wholly or partly removed, when it becomes phosphorus-cleared iron. After boiling has brought the iron to nature, it is wrought iron.

Prior art So-called duplex preparation of wrought iron has been described in patent specifications and treatises and has been attempted in the art, but to the best of my knowledge without successful results.

A reason for this. failure was the removal of too much carbon in the preliminary clearing furnace, so that a sufficient vigorous boil could not be secured in the puddling furnace. One of the resultant evils of this. was the production of excessively oxidizediron, or dryiron. Also, it was necessary to rely unduly upon mechanical agitation to incorporate the slag into the iron for the production of wrought iron. Mechanical agitation without a vigorous boil is not suficient to produce good wrought iron, but is highly desirable to supplement the turbulent mixing occurring as the carbon burns during the boil.

Another serious defect in prior processes was that the slag from the removal of manganese and. silicon was carried over into the puddling furnace, or else the removal of appreciable quantities of these. elements occurred in the puddling furnace, so that at any rate manganeseand silicon-clearing slag became mixed into the finished In the first place, manganese produces a slag having under certain conditions undesirable physical properties when cold. Furthermore, where the. silicic oxide in the slag is due to silicon oxidation from the iron, with its concurrent uncertainties, rather thanv to intelligent addition. of silicic materials to prepare a slag of desirable. physical properties, the slag mixed into the iron will normally be of improper silica content.

Where thev preliminary clearing takes place under conditions of violent agitation, as in a con verter, serious trouble arises. It is very difficult to predetermine the extent to which the oxidizing action will be carried, so that the chemical constitution of the product will be uncertain. In

. spite of all efforts to the contrary, the carbon content may decrease. to such an extent that a vigorous boil in the puddling furnace will be impossible. And, finally, the clearing slag becomes so thoroughly admixed, with the iron that it is carried over into the puddling furnace to a considerable extent, even though a ladle separation be attempted. This slag in the iron is too high in manganese and. silicon.

Preliminary removal of manganese and silicon under basic conditions presents practical difficulty. The lining will deteriorate very rapidly due to slagging with the impurities. Phosphorus will be removed, so that it would be impossible to incorporate the original phosphorus into the slag within the finished wrought iron, and retain the original phosphorus in the finished iron as desired, since this clearing slag must not be carried over into the puddling furnace because of the high manganese and silicon. Furthermore, where manganese is removed under basic conditions, the iron is more highly oxidized than where the clearing is effected under acid conditions.

A further fault of many of the duplex processes previously attempted has been that phosphorus has been removed to an excessive extent in the preliminary clearing operation. Where phosphorus removal has occurred, it is very difficult to retain the high carbon content so necessary for the production of a vigorous boil, for carbon will oxidize after phosphorus at low temperatures.

Furthermore, as the puddling furnace is basic on account of the fettling lining, and will therefore inevitably remove some phosphorus, the phosphorus in the final product may sometimes be too low. It is well known that the presence of phosphorus to a certain extent increases the tensile strength of the iron (American Society of Testing Materials, wrought iron standards) and therefore appreciable phosphorus removal in the preliminary stage, together with the inevitable phosphorus removal in the puddling furnace, may not leave sufiicient phosphorus in the iron.

I believe also that the presence of phosphorus in the slag'which is eventually to be incorporated into the metal has a desirable effect. It would therefore be a mistake to remove much phosphorus in the preliminary furnace, and remove the preliminary clearing slag from the iron, be-

cause the slag mixed with the iron during boiling would then contain little phosphorus.

New process Because of the difiiculty, amounting almost to impossibility, of securing an uncleared iron sufficiently low in manganese and silicon but containing phosphorus and more than 1% of carbon, I contemplate clearing uncleared iron in my first furnace as a step in the manufacture of wrought iron.

I perform this operation under acid conditions in a furnace in which the molten uncleared iron is substantially quiescent during the removal of the manganese and silicon.

I use acid conditions secured by an acid lining in my first, preliminary or clearing furnace be cause the lining would be attacked excessively by the silicic oxide under basic conditions and the metal would be too much oxidized. I avoid turbulence and, therefore, use a substantially quiescent furnace, because of the difficulty of preventing removal of a considerable part of the carbon and burning of the iron if the metal be agitated unduly.

As the puddling furnace I may use either the hand-puddling type, or a mechanical puddling furnace, whether rotary or oscillatory, although I prefer to use mechanical puddling.

Apparatus I have preferred to illustrate my invention by conventional apparatus selected with a view to the excellence of the illustration of the principles involved.

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Figure 1 is a top plan view of furnaces suitable for carrying out my duplex process.

Figure 2 shows the furnaces of Figure l in side elevation.

Figure 3 is a fragmentary section upon the line 33 of Figure 1.

Figure 4 is a fragmentary section upon the line 44 of Figure 1, but with the buggy moved so that it is seen in Figure 4.

Figure 5 is an enlarged section of the preliminary clearing furnace l5, taken upon the line 5-5 of Figure 1.

Figure 6 is a side elevation, half section, of one of the mechanical puddling furnaces seen in Figures 1, 2, 3 and 4.

Figure 7 is a section taken upon the line 'I-7 of Figure 6, showing the mechanical puddling furnace being charged from a ladle. The stack has been omitted in this figure.

Figure 8 is a section corresponding to Figure '7, but showing the furnace rotated to the proper position and having the door open for discharging the wrought iron ball.

Figure 9 is a central longitudinalsection of a hand-puddling furnace adapted for use in my duplex process.

In the drawings like numerals refer to like parts throughout.

Describing in illustration but not in limitation, and referring to the drawings I intend the furnaces shown to be merely diagrammatic, as I do not propose to restrict my invention to any particular furnace design.

Figures 1 and 2 show a preliminary clearing furnace l5 and a group of puddling furnaces 16 adapted to receive iron cleared in the furnace 15. While of course one puddling furnace is all that would be necessary in carrying out my invention, I illustrate several puddling furnaces because they will ordinarily be small, and the furnace will desirably be a large furnace by comparison.

Manganeseand silicon-cleared iron may be transferred in the ladle 17 from the furnace 15 to any one of the puddling furnaces 16. The

, finished wrought iron ball can be removed from any one of the puddling furnaces on the buggy 18.

Instead of transferring directly from the preliminary clearing furnace 15 to a puddling furnace 16, I may intermediately place the iron in any suitable furnace 17, which may be a mixer or storage bath, or a refining furnace, as for manganese and silicon, to remove phosphorus, or to change the constitution of the iron in any other respect.

The furnace 15 may very desirably be a shallowhearth reverberatory as seen more in detail in Figure 5. The iron bath 19 covered by the slag 20 lies on the hearth supported by the lining 21, which will preferably be of silica brick or other refractory which will stand up under acid conditions. The hearth of the reverberatory furnace should be of large horizontal section and shallow depth so as to expose a considerable surface to contact with the air and with the slag above the iron.

For convenience and cheapness I will ordinarily make the roof 22 of magnesite or high grade firebrick, but this is a detail of structure merely.

The furnace will be fired in any suitable manner, as by gas, oil, coal, or powdered coal. I illustrate an oil jet 23 supplied fro-m a pipe line 24 and controlled by a valve 25 because I consider oil firing the most desirable. Air is drawn into the furnace around the jet 23, and, mixing with the fuel, carries the flame over the baffle wall 26 and into the space 27 above the bath.

The entering air may be preheated by passing it through regenerators, recuperators, stoves or checkers, if this be desired, but I do not illustrate any such structure, as it has no part in my invention, and I intend the illustrations to be mer ly diagrammatic.

After passing over the bath, the products of combustion will be carried out the flue 28 and up the stack 29. For the purpose of economy I may run the flue gases through preheating devices for the incoming gases as previously discussed, or may use the flue gases for operating waste heat boilers or in any suitable manner. Since the use of the gases has no bearing upon my invention, I do not illustrate any apparatus for these purposes.

The furnace is provided with a tap hole 30 for the iron and a tap hole 31 for the slag. The iron tap hole should be located a sufficient distance below the slag hole so that there will be no danger of drawing off slag with the iron.

The slag from this reverberatory furnace may be tapped or skimmed from the top of thebath as desired, though preferably I will allow the slag to accumulate during the clearing of a number of iron charges, and remove it only when the quantity of slag becomes excessive.

The furnace 15 may be charged and additions of slagging material may be made through any one of the doors 32 at the side of the furnace.

Iron tapped from the furnace 15 may be transferred to the puddling furnace in the ladle 1'7 supported on the hook 33 from the cable 34 of the crane drum 35. The ladle may be tilted by the chain 36 seen in Figure '7. It would of course be possible to transfer the metal from the furnace 15 to the puddling furnace in any known manner, as in buggies or through troughs, or into an intermediate storage furnace, but this is not important to my invention.

In tapping iron from the furnace 15, I prefer to leave a considerable pool of molten iron continuously in the furnace, to facilitate the clearing of the next charge, to equalize the composition of the iron, and to assist in melting the new charge where the charge is melted in that furnace.

In Figures 1 and 2 I show four mechanical puddling furnaces 16 connected by fiues 37 to stacks 38. The furnaces are mounted above pits 39, provided with inclined slag-removing gratings 40 to carry the wrought iron ball into the buggy 18 running on the track 41, and serving all of the puddling furnaces. The buggy will carry the completed ball to the squeezer and rolls, not shown.

The arrangement of the pairs of mechanical puddling furnaces with respect to the gratings, buggy, and stacks may be best seen in Figures 3 and 4.

In Figure 6 my mechanical puddling furnace may be seen in more detail. The outer metal casing 42 gives mechanical support to the heat insulation 43 and to the furnace lining 44, which may be of any material adapted to stand up under basic conditions, as for example magnesite.

The furnace bottom of slag is seen at 45 cover- 7 stiffeners 49 brace the furnace body from the hubs.

Air and fuel enter the furnace through an opening 50 near the axis at one end. I may use any suitable type of fuel, but prefer gas, oil, or powdered coal. In the drawings I show an oil jet 51 supplied from the pipe line 52 and controlled by a valve 53.

Combustion takes place in the body of the furnace above the charge, and the products of combustion pass out through the neck 54 into the flue 55 and thence to the stack 38. The flue is suitably sealed to the neck so that the furnace may be rotated or oscillated without excessive loss of draft from the stack.

For rotation or oscillation of the furnace I provide a suitably geared driving band 56, upon which a motor 57 operates by means of the geared connection 58.

The furnace door 59 may be very desirably power controlled for convenience in operation. The position of the door, at the side of the furnace, is merely a convenient placing, and is not intended to limit the apparatus to this form. In Figures 6, 7 and 8 I show the door, consisting of a refractory lining 60 and structural support 61, attached to the bracket 62, which is hinged at 63 to the furnace body and at 64 to the structural support.

The bracket 62 may be moved in and out by rotation of the screw 65, connected to the bracket at 66 and operated through the geared connection 67 from a driving motor 68 mounted on the furnace body.

In Figure 7 I show the mechanical puddling furnace in charging position. The furnace has been rotated so that the door 59 is near the top, and the door is open. The ladle 17 may be placed close to the door so that the charge can be poured into the furnace by tilting the ladle from the tilting chain 36.

In Figure 8 I show the mechanical puddling furnace discharging a puddled ball. The furnace has been rotated so that the door 59 is near the bottom and above the grating 40, and the door has been opened, so that the ball may fall upon the grating and roll into the buggy.

In Figure 9 I show a hand puddling furnace adapted to be used instead of the mechanical ftn'nace in performing the puddling operation. The hearth 69 for receipt of the metal may be lined with any suitable refractory material, such as magnesite, and then covered with fettling. The furnace is roofed as at 70 with suitable refractory material.

Air is drawn in through the opening 71, either directly from the atmosphere or preheated as desired, and is carried through the grate 72 and the coal fire 73 over the baflie wall 74 and above the charge. After the products of combustion have passed over the charge they are led through the flue 75 and up the stack 76. The charge may be worked through the work door 77 in the side of the furnace.

The structural details of the furnace are not important. Figure 9 need not necessarily be a typical puddling furnace, since my invention may be employed with any furnace, no matter what the shape of the hearth, providing the mechanical working characteristic of puddling may be there performed.

The process In carrying out my process it is of course possible to obtain advantage from any of the novel steps which I use without employing the others (though they cooperate to secure a common result), or without operating under the most advantageous conditions, and I intend to protect any mode of operation involving my broad invention. For the purpose of complying with the statute and with no intention to limit my invention to the specific operations discussed, I will now outline briefly the detailed procedure which I employ in the best embodiment of my invention known to me.

Before describing my process further it is well to keep in mind the following important steps performed by me:(l) clearing of manganese and silicon in a separate substantially quiescent acid-lined reverberatory furnace; (2) separation of the manganeseand silicon-cleared iron from the manganeseand silicon-clearing slag without mixture of the slag into the body of the iron; (3) removal of all or part of the phosphorus at moderate temperature during a quiescent period at the beginning of the puddling operation; (4) utilization of a carbon content in excess of 1% and preferably in excess of 3% to produce a violent boil; (5) incorporation of a phosphorus clearing slag into the iron during the boil.

The initial clearing of manganese and silicon will be carried out in a first furnace which may very desirably be a reverberatory or air furnace. The iron will then be placed in a transfer ladle and carried to a puddling furnace, which may be of the fiat-hearth hand-puddling type, or more desirably a mechanical oscillatory or rotary puddling furnace.

As a first furnace I prefer to use an acid-lined shallow-hearth reverberatory into which the uncleared iron may be charged, either cold or hot, as previously explained. Where the process is carried out at some distance from the blast furnace it will be necessary to charge the iron cold and melt it before clearing.

As soon as the iron has been melted, if it be charged cold, or as soon as charging is complete, if it be charged hot, I add iron oxide, preferably in the form of roll or hammer scale, or iron ore, to the bath. Other basic additions may be made, but the total basic material should not be sufficient to make the resulting slag predominantly basic.

The bath is then maintained substantially quiet for a sufiicient period in contact with the slag in the furnace, and below the atmosphere of air and products of combustion. The temperature will, of course, vary with the character of the uncleared iron which I am treating and with the extent of elimination of impurities which I desire, but I find a temperature of about 2500 F. satisfactory in ordinary operation. During this period of quiet exposure to the atmosphere in the air furnace, the silicon and manganese in the iron will be oxidized to the extent desired and will combine with the slag, yielding some additional heat to the bath.

Some removal of sulphur will occur in my preliminary clearing furnace and also in the puddling furnace, but generally this is of minor importance.

It will be noted that since my first furnace has an acid lining, no appreciable removal of phosphorus will occur there.

It will be further evident that I do not carry the oxidation in the first furnace to a point where appreciable carbon removal will take place, since it is particularly important that the carbon content of the iron charged into the puddling furnace be in excess of 1% about 3%.

After a sufiicient period of purification of the bath I tap from the manganeseand siliconcleared iron, below the slag line, a sufficient charge for one puddling furnace. Thus I prefer to retain a residue of manganeseand siliconcleared iron in the furnace, and to add to that fur-- ther uncleared iron for purification, so that the subsequent purifying periods will be much shortened because of the dilution of the impurities in the manganeseand silicon-cleared iron. This, however, is not an essential feature of my invention, and I might operate effectively, though less desirably, by completely emptying the first furnace of manganese and silicon-cleared iron before adding a further charge.

The iron contained in my transfer ladle will be free from the manganeseand silicon-clearing slag of the first furnace because the quiescent conditions in the first furnace prevent any considerable admixture of slag with iron at any time, the iron is tapped from a point considerably below the slag level, and the bath will normally not be lowered during tapping to such a point that the slag level approaches the iron tap hole.

The retention of phosphorus is not only desirable for use in the second furnace but seems to protect the carbon and the iron in that phosphorus oxidizes preferentially to carbon and iron at low temperatures and so permits transfer of the iron and its charging into the puddling furnace without excessive oxidation of carbon or iron.

I have indicated that phosphorus protects the carbon and iron from oxidation. Of course, it is Well known that under basic conditions and at comparatively low temperatures phosphorus will oxidize in preference to carbon. While I do not wish to be limited to any theory herein presented, it is my belief that phosphorus also protects the iron and carbon from oxidation during the transfer interval from one furnace to another, and in this respect I believe that the phosphorus inhibits oxidation; or, stated in another way, increases the resistance to hot oxidation of the metal.

While it is thoroughly feasible to use my manganeseand silicon-cleared iron in a hand puddling furnace, the operation in a mechanical puddling furnace is so much more desirable that I Will describe it as my preferred form. The mechanical puddling furnace, normally lined with magnesite or other similar material which will stand up under basic conditions, will ordinarily be operated intermittently, one ball being produced during each cycle of operation.

The furnace will first be heated, preferably by oil, gas or powdered fuel, and one or more bottoms will be made up in the interior. The bot toms will normally be prepared from a mixture of iron oxides and silicates, fused together, and therefore will be strongly basic. I prefer to mix together roll scale and iron purifying-cinder (slag). Roll scale alone is too oxidizing for the best results in that it precipitates the boil rather and preferably early in the process, while cinder alone is not sufficiently oxidizing to remove phosphorus to the best advantage.

The cinder which I use may very desirably be that obtained from a steel refining furnace, or may even be that from my own first furnace which has been analyzed and mixed with the requisite roll scale to properly regulate its silica and manganese content. I prefer not to use the slag from my first furnace, however, because of the presence of the undesirable manganese, even though the silica be properly adjusted.

I must, of course, be careful in choosing my roll scale that I do not add objectionable quantities of manganese which might find its way into the iron, because my puddling furnace will normally be operated so as not to remove large amounts of manganese.

Instead of or in addition to roll scale or cinder I may use other basic materials in my puddling furnace, such as high grade iron ore, limestone, salts of the alkali metals or similar material.

The bottom should form a thorough coating for the lining where magnesite is used as a lining material, because otherwise magnesium oxide will be absorbed into the slag, producing an undesirable slag under some conditions.

In the preparation of my bottom it is not alone sumcient to keep in mind the removal of phosphorus and the retention of carbon during the phosphorus removal. The slag forming my bottom, after absorbing phosphorus and some iron from the charge, will be incorporated into the muck bar. Therefore I must be particularly careful that the slag is of desirable physical properties, especially when cold. A very satisfactory slag, which I give as an example of permissible practice, contains among other things, about FeO, 12% SiOz, 1% P and 1% MnO. Of course, slags can be made up by those skilled in the art, so long as my essential conditions are preserved.

Having made up one or several bottoms in the puddling furnace, I charge manganeseand silicon-cleared iron from the ladle. It is not necessary to heat during this operation.

After the charging has been completed, the puddling furnace charge is allowed to stand quiescent and at moderate temperature for a short period, usually about ten minutes. This quiescent period is very important in my process, because it is during this time that I remove phosphorus. The low temperature and absence of any objectionable agitation while under basic oxidizing conditions I find admirably suited for the purpose of phosphorus removal into the slag.

During the quiescent period the iron is covered by the slag which comprises my bottom. The quiescence, low temperature, slag covering and only moderately oxidizing conditions of the slag will combine to prevent carbon from coming out. Carbon must not oxidize at this time, because if appreciable carbon starts to oxidize phosphorus removal will be interfered with.

As the last of the phosphorus is removed, some carbon will inevitably oxidize, and this constitutes a further reason why it would be undesirable to take out the phosphorus to any appreciable extent in a first step, because the carbon removal would then take place where it could not be used to produce the boil.

Although I consider it to be less desirable, some advantage from my method might be obtained by removing the phosphorus in a furnace preliminary to the puddling furnace, which I generally indicate as 17. The same conditions, as for example basic slag and low temperature, should there prevail.

Many specifications as to quality of wrought 145 iron require high phosphorus. For example, the American Society for Testing Materials, specifies that phosphorus should be above 0.15% on accountof the increased tensile strength. My invention makes such requirements easy to fulfill. 15g

Some phosphorus removal in the puddling fur nace is inevitable on account of the basic conditions, and, by avoiding the elimination cf phosphorus in the preliminary clearing furnace, I can permit some phosphorus removal in the puddling furnace and still have a final muck bar high in phosphorus.

By suddenly raising the temperature, I can change the action of oxygen so that it will combine with carbon instead of phosphorus, and this selective action enables me to conveniently control the residual elemental phosphorus content in the muck bar.

After the quiescent period, practically no more phosphorus will be removed during puddling, and therefore I will be careful that the additions of roll scale or other oxidizing or slag-forming materials during the remainder of the puddling are reasonably free from phosphorus, or else that the phosphorus enrichment from such sources is considered in predetermining the composition of the resultant muck bar. Steel roll scale may very desirably be used at this point in preparing muck bar low in phosphorus.

At the end of the quiescent period I heat the charge and add iron oxide, preferably in the form of roll scale, for the purpose of producing the boil. Agitation is started during the roll scale addition; and after the addition has been completed the charge should be violently mixed. The iron oxide will cause carbon to oxidize, producing a violent ebullition of gases, chiefly carbon monoxide. The bubbling of the gases through the metal, as well as the mechanical operation of the mixer, will combine to incorporate the slag thoroughly into the iron.

After the'boil has been completed I run off the surplus slag, preferably by inverting the mixer and opening the door a small distance, sumcient to allow the slag to run through, but designed to retain the now pasty metal.

Violent agitation is continued until the puddled ball has been formed, and then the ball is taken to the squeezer and the rolling mill as in the prior practice.

Where, instead of a mechanical, I use a hand puddling furnace, the theoretical operation is identical. I make up a slag in the hand puddling furnace on the fettling lining, and charge -my manganeseand silicon-cleared iron into the furnace.

The manganeseand silicon-cleared iron charged is preferably molten, but it may be charged 'cold and melted in thepuddling furnace. The iron could even be charged cold into the mechanical puddling furnace, and melted therein, but this would hardly be desirable.

The first step (after melting, if'that be performed) is the quiescent period for phosphorus removal, as in the mechanical puddling furnace. Then the iron is agitated and iron oxide added to produce the boil. Working should continue until the iron begins to come to nature. Then the excess of slag is removed (though it is very diflicult to remove it as completely as in the mechanical puddler), and the ball formed.

It will be evident that this-process in no wise differs'fr'om the mechanical puddling process according to my invention, except that the labor of the puddler instead of the machine must work 7 the iron.

In view of my invention and disclosure variations and modifications tomeet individual whim or'particular'need will doubtless become evident to others skilled in the art, to obtain. part or all of the benefits of my invention without copying the structure shown, and I, therefore, claim all such in so far as they fall within the reasonable spirit and scope of my invention.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In the duplex manufacture of wrought iron, the method which consists in removing manganese and silicon from molten iron containing more than 1% of carbon and a substantial amount of phosphorus under quiescent acid conditions while retaining substantially the initial content of phosphorus in the iron, and puddling the manganeseand silicon-cleared iron under basic conditions.

2. In the duplex manufacture of wrought iron, the method which consists in treating molten iron containing more than 1% of carbon and a substantial amount of phosphorus under quiescent conditions within an acid lining, to remove manganese from the iron and to retain phosphorus in the iron, in adding basic ingredients within the slag to absorb silicon oxidized from the iron, the quantity of basic ingredients being insuiiicient to-make the slag predominantly basic and in stopping the operation while the carbon of the iron is substantially unoxidized.

3. In the duplex manufacture of wrought iron,

the method which consists in preliminarily removing impurities from molten iron containing more than 1% of carbon and a substantial amount of phosphorus under acid conditions while retaining substantially the initial phosphorus and carbon contents of the iron during thepreliminary clearing and using the phosphorus retained to protect the carbon and iron from oxidation, separatingthe iron from the clearing slag and puddling the preliminarily cleared iron under basic conditions.

4. In the duplex manufacture of wrought iron, the method which consists in preliminarily -removing impurities of molten iron containing more than 1% of carbon and a substantial amount of phosphorus, retaining substantially the initial phosphorus content-of the ironduring theoperation, puddling the preliminarily cleared iron, and using the phosphorus retained in the iron to allow for partialphosphorus removal and provide a muck bar high in phosphorus.

5. In the duplexmanufacture of wrought iron, the method which consists in removing manganese and silicon from molten iron containing more than 1% of carbon and a substantial amount of phosphorus, while retaining substantially the initial: phosphorus contentduring the operation, subsequently removing phosphorus at moderate temperature under quiescent basic conditions and puddling the phosphorus-cleared iron.

6. In the duplex manufacture of wrought iron, the method which consists in slagging molten, uncleared iron containing a substantial amount ofphosphorus under acidconditions, in thus removing manganese and silicon from the uncleared iron, retaining substantially the initial phosphorus'content during the slagging operation, separating the clearing'slagfrom the iron, removing phosphorus from the iron by 'basically slagging the iron under quiescent'oxidizing conditions at low temperature, protecting the carbon from early oxidation by control of the conditionswhile' removing thephosphorus, and puddling the phosphorus-cleared iron.

'7. In the duplex manufacture of wrought iron,

the method which consists in eliminating the manganese and silicon to be removed from the uncleared iron and a substantial amount of phosphorus under acid conditions preliminary to puddling, while avoiding substantial phosphorus removal, in separating the manganeseand silicon-cleaning slag from the iron and in eliminating the phosphorus to be removed from the iron under basic conditions in the presence of a mildly oxidizing iron silicate slag containing an excess of iron oxide.

8. In the duplex. manufacture of wrought iron, the method which consists in removing manganese from molten iron containing more than 1% oi carbon and a substantial amount of phosphorus under quiescent acid conditions while retaining the phosphorus and a carbon content in excess of 1%, subsequently removing phosphorus under basic conditions while retaining a carbon content in excess of 1% and boiling the iron by virtue of the oxidation of the carbon.

9. In the duplex manufacture of wrought iron, the method which consists in removing manganose from molten iron containing more than 1% of carbon and substantial amount of phosphorus under qu'escent acid conditions while retaining the phosphorus and a carbon content in excess of 1%, subsequently removing phosphorus under basic conditions while retaining a carbon content in excess of 1%, boiling the iron by virtue of the oxidation of the carbon and concurrently mechanically mixing the iron.

19. In the duplex manufacture of wrought iron, the method which consists in removing manganese and silicon from molten iron containing more than 1% 01" carbon and a substantial amount of phosphorus under acid conditions while retaining the phosphorus and a carbon content in excess of 1%, removing the phosphorus under basic conditions while retaining a carbon content in excess of 1%, boiling the iron by virtue of carbon oxidation and concurrently turbulently mixing the iron.

11. In the duplex manufacture of wrought iron, the method which consists in removing inanganese and silicon from molten iron containing more than 1% or" carbon and a substantial amount of phosphorus, under acid conditions, while retaining a carbon content in excess of 1%, separating the manganeseand silicon-clearing slag from the iron, removing the phosphorus, and boiling the iron by virtue of carbon oxidation.

12. In the duplex manufacture of wrought iron, the method which consists in removing manganese and silicon from molten iron containing more than 1% of carbon and a substantial amount of phosphorus while retaining a carbon content in excess of 1%, separating the manganeseand silicon-clearing slag from the iron, removing the phosphorus and boiling the iron by virtue of carbon oxidation in the presence of the phosphorus-clearing slag.

13. In the mechanical puddling of iron, the method which consists in incorporating a slag containing less than 2% of manganese and more than 0.5% of phosphorus into the iron by vigorously boiling and by flowing the metal to cause it to lap over itself.

14. In the duplex manufacture of wrought iron, the method which consists in removing manganese and silicon from molten iron containing more than 1% of carbon and a substantial amount of phosphorus under quiescent acid conclitions While retaining phosphorus and a carbon content in excess of 1%, separating the iron from the maganeseand silicon-clearing slag, removing phosphorus under quiescent basic conditions, retaining some phosphorus clearing slag in contact with the iron and boiling the iron by virtue of oxidation of the carbon to incorporate the phosphorus clearing slag into the iron.

CHARLES HART. 

